Many internal combustion engine utilize Gasoline Direct Injection (GDI) to increase the power efficiency and range over which the fuel can be delivered to the cylinder. One potential issue with GDI is that under lower injection pressures the fuel may not sufficiently mix with the air in the cylinder. Insufficient mixing may decrease engine power and efficiency, and increase emissions, at least under some conditions. For example, during cold engine starts, and before the catalytic converter is activated, insufficient mixing may exacerbate cold start emissions.
One approach to provide more rapid pressure rise during engine starting (e.g., before the high pressure pump is able to provide sufficient pressure increase) may include utilizing a method for generating a high pressure wave, such as a fluid hammer, that propagates downstream of the high pressure pump through into the fuel rail. The fluid hammer can occur when the motion of the fluid in a passageway is forced to stop or change direction suddenly.
Thus, while many attempts may take actions to mitigate such high pressure waves, the above approach uses the wave to increase the pressure in the fuel rail before engine start up. By utilizing the high pressure wave created by the fluid hammer to increase the pressure in the fuel rail before or during start up of the lift pump located in the fuel tank, and before full activation of the high pressure pump, it is possible to obtain increased pressure rise. This can lead to decreased lift pump size, and increased overall fuel system efficiency.